Chain-type door fastening device

ABSTRACT

A chain-type door fastening device mounted on the door jamb and integrated into the strike plate assembly of the conventional door knob and latch. The chain-type door lock comprises a loop of chain that can be slipped over the door knob when the door is closed, allowing the door to be opened a few inches so the occupant can scrutinize a caller. However, there is also provided a chain locking means in the form of a pawl for engaging a link of the chain to shorten the loop of chain when the door is closed, thereby precluding the opening of the door even if the other latch is opened.

limited States atent [191 [111 3,809,218 Canllield May 7, 11974CHAIN-TYPE DOOR FASTENING DEVICE Primary Examiner-George V. Larkin [75]Inventor: g g Canfield Albuquerque, N $212253 gggilzgttor Firm-Schuyler,Birch, Swmdler,

[73] Assignee: Tuflok, lnc., Albuguerque, N. Mex. 57 ABSTRACT [22]Filed; Jan, 2, 1973 A chain-type door fastening device mounted on thedoor jamb and integrated into the strike plate assem- [211 App! 320606bly of the conventional door knob and latch. The chain-type door lockcomprises a loop of chain that [52] US. Cl. 292/264 n be lipp ver thedoor knob when the door is [51] llnt. Cl. 1E05c 19/08 closed. allowing tdoor t be open d a few inches so [58] Field of Search 292/262, 264;70/93 the occupant can scrutinize a caller. However, there is alsoprovided a chain locking means in the form of a [56] References Citedpawl for engaging a link of the chain to shorten the UNITED STATESPATENTS loop of chain when the door is closed, thereby pre- 3,640,5582/1972 Read et al 292/264 Fludmg 3 openmg Ofthe door even If the otherlatch 2,790,663 4/1957 Sarver 292/264 Opene 27 1 I 24 ill I 2sr 25 r/ 8Claims, 3 Drawing Figures BACKGROUND OF THE INVENTION This inventionpertains generally to door locking systems and more particularly tochain-type door fastening means.

In order to provide optimum security for the occupant of a room it isnecessary that a door be equipped with three locking systems:

1. A conventional door knob operated lock having a latch spring biasedto the engaged position and movable to the disengaged position byoperating the door knob. These latches typically are key-lockable, andthe latch engages a strike plate installed in the door jamb.

2. A dead-bolt type lock on the inside of the door. This lock is notoperable from outside of the room.

3. A safety chain that allows the occupant to open the door a few inchesto allow the occupant to see and converse with a caller, withoutallowing the door to be forced completely open.

The requirement for the above three types of locks is particularly truein hotels, motels and like establishments. In the past, it has beencommon to attach to the doors of such commercial establishments threeseparate locking means for performing the above three functions. Such anarrangement is expensive to install and maintain, and the occupant mustconcern himself with the three separate devices.

Furthermore, travelers are concerned with providing a positive, tamperproof lock on the door ofa commercial establishment. Quite often,dead-bolts are not installed, or are inoperable, or a type of bolt lockis used that can actually be opened by the management. In this case,entry can be gained by use ofa stolen master key, for example. While theprior art has portable devices for positively locking doors from theinside, such as wedges and poles, these can easily be improperlyinstalled, and thus their effectiveness is questionable.

SUMMARY OF THE INVENTION The chain-type door fastening device of thisinvention performs the function of both a dead-bolt lock and a safetychain. It can also be presented as a portable unit that can be easilytemporarily installed and removed.

The device constructed in accordance with this invention comprises aplate which is attached to the door jamb and which may be integral withthe normal strike plate that is engaged by the door knob operated latch.Attached to the plate is a loop of chain of such length as to allow itto be slipped over the door knob when the door is closed. Then, when thedoor is opened, the chain is pulled taut about the stem of the doorknob, allowing the-door to be opened an amount sufficient to allow theoccupant to see and converse with a caller. Also installed on the plateis a lock means that can be engaged by one of the links of the chain.Thereby, when the door is completely closed, the slack in the chain thatwould otherwise be present and allow the door to be opened slightly canbe removed by pulling the chain taut and engaging the locking means withthe appropriate link in the chain. In other words, the length of theloop is shortened. Thus, the door cannot be opened from the outside evenif the knob operated latch were released.

This invention is easily installed and can be used with most doors. Itfunctions as and replaces two elements: the dead-bolt lock and thesafety chain. It is simple and effective, yet requires no maintenance.In its portable form it supplements existing locking devices.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of apreferred embodiment of the invention integrated with the strike plate;

FIG. 2 is a top view, partially in section, showing the device of FIG. 1in one of the operating conditions; and

FIG. 3 is a perspective view of the device of FIG. 1 in the otheroperating condition.

DESCRIPTION OF THE PREFERRED EMBODIMENT The invention is described withregard to a conventional door 10 and door frame 11. The inventioncomprises a strike plate 12, a lock plate 14, and a chain at tachmentplate 16. A chain, the details of which are explained below, is attachedto chain plate 16.

The conventional door frame 11 includes a door jamb surface 19 facedwith a molding strip 20. Normally, a conventional strike plate (notshown) would be installed in door jamb 19. Strike plate 12 of theinventive device replaces the conventional strike plate and duplicatesthe functions thereof. Strike plate 12 is of rectangular shape and isprovided with a plurality of openings through which screws 22 pass toattach the inventive device to door jamb surface '19. Strike plate 12 isalso provided with an opening 24 for engaging the conventional door knoboperated latch 23. Opening 24 typically presents on three sides edges25, 26 and 27 on the fourth side a flange 28 perpendicular to opening 24which the door latch engages. Adjacent to opening 24, cut into door jambsurface 19, is a box-like recess 30 for receiving latch 23. It should beunderstood that strike plate 12 can be of other designs, as necessary toaccommodate other types of door latches.

A lock plate 14 is attached to or integral with strike plate 12. Lockplate 14 is at an angle to strike plate 12 outwardly of the door openingin order to engage and cam inwardly the door latch 23, and also in orderto space chain plate 16 outwardly of the door opening so that chain 40is not easily caught between door 10 and frame 11.

Chain plate 16 is attached to or integral with lock plate 14. Lock plate14 is provided with a pair of cutout portions 31 and 32, and chain plate16 is provided with a pair of cut-out portions 33 and 34, adjacent ofthese openings defining upstanding chain shortening and fastening pawls37 and 38. The size and shape of pawls 37 and 38 accommodate the link 41of chain 40. Pawl 37 is used when the device is installed on doorsopening to the left, and pawl 38 on doors opening to the right, with theentire device being turned around.

A loop of chain 40 having a plurality of links 41 is attached to chainplate 16 by means such as a pair of screws 42 extending through openingsin chain plate 16 and secured by nuts 43. Chain 40 must be at least ofsuch length as to slip over knob 52.

A complete understanding of the invention can best be grasped by adiscussion of the operation of the device. First of all, looking to FIG.2, a door 10 is provided with a conventional lock set including doorknobs 51 and 52 having neck portions 53 and 54, and being mountedrespectively on knob plates 55 and 56. Door knobs 51 and 52 areinterconnected with each other and operate latch 23 in the conventionalmanner. Likewise, in conventional manner, latch 23 is provided with aninclined surface 58, an end surface 59, and a side surface 60.Conventionally, latch 23 is springloaded to the position shown in FIG.2.

In order to utilize the inventive device, the door is first closed tothe position shown in phantom in FIG. 2. As door 10 is closed, latch 23is cammed inwardly by lock plate 14 until latch 23 finally seats inrecess with side surface 60 in engagement with flange portion 28 ofstrike plate 12. Chain is then slipped over door knob 52, so that it isdraped around neck 54. The length of chain 40 must be at leastsufficient to pass over door knob 52 without effort, but need be nolonger. The maximum length of chain 40 should be such that chain 40cannot be slipped over knob 52 unless door 10 is fully or almost fullyclosed. With chain 40 loosely draped over neck portion 54, door 10 canbe opened to the point shown in solid lines in FIG. 2, about 1 or l /2inches. In such a position, chain 40 is drawn tightly about neck portion54. The door 10 is now open to sufficient distance to allow the occupantto observe and converse with a caller. However, door 10 cannot be fullyopened, nor can chain 40 be disengaged from door knob 52. Pushing on theoutside of door 10 simply increases the tension of chain 40. Screws 22are preferably of the one-way type, so that one cannot easily remove theentire strike plate 12 when door 10 is ajar as is shown in FIG. 2. Thus,the invention fulfills a superlative manner the functions of theconventional safety chain.

However, this inventive device also functions as a dead-bolt lock.Looking now to FIG. 3, when door 10 is fully closed, the loop of chain40 is slipped over knob 52 and is pulled taut. Then, the appropriatelink 41 of chain 40 is engaged with pawl 37. This shortens the loop ofchain 40 and holds door 10 closed even if latch 23 is retracted. Effortsto force the door 10 when latch 23 is retracted are resisted by screws22 and by flange The inventive device is shown herein as a permanent 1installation, replacing the conventional strike plate normally found inthe door jamb, and replacing the usual dead-bolt and safety chain.However, it should be noted that the basic principles of the inventionare also applicable to a portable device which functions in addition toall other locks. The portable device functions as a dead-bolt. In thisportable embodiment, the device is exactly as pictured. However, it neednot have openings for screws 22. To install the portable device, door 10is opened, and strike plate 12 is superimposed upon the existing strikeplate in the door frame (not shown), so that flange 28 protrudes intothe opening of the existingstrike plate. Door 10 is then closed, withstrike plate 12 interposed between the existing strike plate and theedge of door 10. The device is thus held firmly in place by theengagement of flange 28 with the existing strike plate and cannot beremoved so long as door 10 remains closed. Lock plate 14, chain plate16, and chain 40 extend into the room. Chain 40 is then slipped 6 overknob 52 and is drawn taut, and then an appropri- 5 ate link 41 isengaged, with pawl 37, in the same manner as with the permanentembodiment.

To one skilled in the art, a number of variations and modifications ofthe above described preferred embodiment of the invention may come tomind. For example, while a pair of pawls 37 and 38 have been shown toengage links 41 to hold chain 40 taut, other means could be used, suchas slots into which a link 41 could be slipped. Likewise, lock plate 14and chain plate 16 need not be integral with strike plate 12, but anormal strike plate can be used and chain attachment plate 14 can beattached directly to the door frame. However, the basic principles ofthe invention still apply. It should therefore be understood that theinvention is not to be limited to the preferred embodiment describedabove but is governed in scope only by the scope of the appended claims.

What is claimed is:

1. A chain-type door fastening device for use with a door having a doorframe and a door knob, said device comprising:

chain means and means for attaching said chain means to said door frameat a point substantially in alignment with said door knob and adjacentto said door knob when said door is in the closed position against saiddoor frame, said chain means being disposed in a loop extendableoutwardly from said door frame, said loop being of a first lengthsufficient to extend about said door knob when said door is in saidclosed position, and

chain shortening and fastening means attachable to said door frame andengageable with said chain means for shortening said chain means todefine said loop in a second length shorter than said first length andto fasten said chain in said short length. whereby said loop can bedrawn taut about said door knob to said second length and fastenedthereat when said door is in said closed position to preclude opening ofsaid door, said door being openable a small amount when said loop isdisengaged from said chain shortening and fastening means.

2. The chain-type door fastening means of claim I wherein said doorframe has a recess for receiving a door knob operated latch meansinstalled on said door, and wherein said means for attaching said chainmeans comprises flange means extendable into said recess and engageabletherewith.

3. The chain-type door fastening device of claim 1 wherein said meansfor attaching said chain means comprises a chain mounting plate, saidchain means and said chain shortening and fastening means being attachedto said chain mounting plate.

4. The chain-type door fastening device of claim 3 wherein said chainshortening and fastening means comprises a pawl engageable with saidchain means.

5. The chain-type door fastening device of claim 3 wherein said meansfor attaching said chain means further comprises a strike plate mountedon said door frame and engageable with door knob operated latch meansinstalled on said door, said chain mounting plate being attached to saidstrike plate.

6. The chain type door fastening device of claim 5 wherein said doorframe has a recess for receiving door knob operated latch meansinstalled on said door and wherein said strike plate comprises:

a strike plate opening aligned with said recess, and

a flange attached to said strike plate along that edge of said strikeplate opening that lies in the direction said door opens, said flangebeing substantially perpendicular to said strike plate and extendinginto said recess.

7. The chain-type door fastening device of claim 3 wherein said chainmounting plate is spaced laterally from the line of travel of the edgeof said door whereby said chain when hanging from said chain mountingplate hanges spaced from said door so as not to inhibit movement of saiddoor.

8. A chain-type door fastening device for use with a 1 cess, a lockplate attached to said strike plate and extending outwardly therefrom inthe direction said door opens, said lock plate having a portion inclinedaway from said door to cam said door knob operated latch means inwardlyas said door is closed, and a chain mounting plate attached to said lockplate,

a loop of chain attached to said chain mounting plate, said loop beingofa first length sufficient to extend about said door knob when saiddoor is in the closed position, and

chain shortening and fastening means mounted on said chain mountingmeans and engageable with said chain to shorten said loop to a secondlength closely about said neck portion of said door knob, whereby whensaid loop is in said first length said door can be partially opened, butwhen said loop is in said second length said door is fastenedsubstantially in the closed position.

1. A chain-type door fastening device for use with a door having a doorframe and a door knob, said device comprising: chain means and means forattaching said chain means to said door frame at a point substantiallyin alignment with said door knob and adjacEnt to said door knob whensaid door is in the closed position against said door frame, said chainmeans being disposed in a loop extendable outwardly from said doorframe, said loop being of a first length sufficient to extend about saiddoor knob when said door is in said closed position, and chainshortening and fastening means attachable to said door frame andengageable with said chain means for shortening said chain means todefine said loop in a second length shorter than said first length andto fasten said chain in said short length, whereby said loop can bedrawn taut about said door knob to said second length and fastenedthereat when said door is in said closed position to preclude opening ofsaid door, said door being openable a small amount when said loop isdisengaged from said chain shortening and fastening means.
 2. Thechain-type door fastening means of claim 1 wherein said door frame has arecess for receiving a door knob operated latch means installed on saiddoor, and wherein said means for attaching said chain means comprisesflange means extendable into said recess and engageable therewith. 3.The chain-type door fastening device of claim 1 wherein said means forattaching said chain means comprises a chain mounting plate, said chainmeans and said chain shortening and fastening means being attached tosaid chain mounting plate.
 4. The chain-type door fastening device ofclaim 3 wherein said chain shortening and fastening means comprises apawl engageable with said chain means.
 5. The chain-type door fasteningdevice of claim 3 wherein said means for attaching said chain meansfurther comprises a strike plate mounted on said door frame andengageable with door knob operated latch means installed on said door,said chain mounting plate being attached to said strike plate.
 6. Thechain type door fastening device of claim 5 wherein said door frame hasa recess for receiving door knob operated latch means installed on saiddoor and wherein said strike plate comprises: a strike plate openingaligned with said recess, and a flange attached to said strike platealong that edge of said strike plate opening that lies in the directionsaid door opens, said flange being substantially perpendicular to saidstrike plate and extending into said recess.
 7. The chain-type doorfastening device of claim 3 wherein said chain mounting plate is spacedlaterally from the line of travel of the edge of said door whereby saidchain when hanging from said chain mounting plate hanges spaced fromsaid door so as not to inhibit movement of said door.
 8. A chain-typedoor fastening device for use with a door having a door frame, a doorknob having a neck portion and door knob operated latch means, and arecess in said door frame for receiving the door knob operated latchmeans, said device comprising: chain mounting means comprising a strikeplate attachable to said door frame, said strike plate having a strikeplate opening alignable with said recess and a flange attached alongthat edge of said strike plate opening that lies in the direction saiddoor opens, said flange being substantially perpendicular to said strikeplate and extendable into said recess, a lock plate attached to saidstrike plate and extending outwardly therefrom in the direction saiddoor opens, said lock plate having a portion inclined away from saiddoor to cam said door knob operated latch means inwardly as said door isclosed, and a chain mounting plate attached to said lock plate, a loopof chain attached to said chain mounting plate, said loop being of afirst length sufficient to extend about said door knob when said door isin the closed position, and chain shortening and fastening means mountedon said chain mounting means and engageable with said chain to shortensaid loop to a second length closely about said neck portion of saiddoor knob, whereby when said loop is in said first length said door canbe partially opened, but when said loop is in said seconD length saiddoor is fastened substantially in the closed position.